We have just finished configuring L2TP VPN access for a remote Juniper SSG-5 security appliance. We have properly imported the certs (using the Certificates MMC), and are now attempting to connect to the VPN using the provided Microsoft VPN client (under Control Panel > Network Connections > New Connection Wizard). We've altered the settings on the Windows VPN client to be L2TP'/IPSec, but when we attempt to connect, we get the following error: